Effects of Copper Content and Mold Temperature on the Hot Tearing Susceptibility of Mg-7Zn-xCu-0.6Zr Alloys

The effects of copper (Cu) content and mold temperature on the hot tearing susceptibility (HTS) of Mg-7Zn-xCu-0.6Zr (x = 0, 1, 2) alloys were investigated experimentally using a T-type hot tearing mold. The crack volumes were measured by paraffin permeation method, and the solidification process was analyzed by thermal analysis and by using the Clyne and Davies model. The microstructure and morphology of the crack zone of Mg-7Zn-xCu-0.6Zr alloys were characterized by scanning electron microscopy, and the composition of alloys was analyzed by X-ray diffraction. The results showed the formation of a new phase of MgZnCu in the alloys with Cu addition. Moreover, addition of Cu also led to the refinement of microstructures of Mg-7Zn-xCu-0.6Zr alloys. The HTS of Mg-7Zn-xCu-0.6Zr alloys decreased with the increase in both the content of Cu and the mold temperature.